If you are measuring Re this is for earth rods on a TT.
To measure Zs use F3 to remove Re.
From the manual:
No trip, RCD in circuit
1. Turn the rotary switch to the Z| NO TRIP position.
2. Connect all three leads to the L, PE, and N (red, green, and blue)
terminals of the tester.
3. Press F1 to select L-PE. The display shows the ZL and no trip
indicator. (Do not press F3, as this will select RE)
4. Before you do a loop impedance test, use the zero adapter to zero the
test leads or the mains cord. Press and hold ‘zero’ for more than two
seconds until the ZERO annunciator appears. The tester measures
the lead resistance, stores the reading in memory, and subtracts it
from readings.
5. Connect all three leads to the L, PE, and N of the system under test or
plug the mains cord into the socket under test.
6. Press and release ‘Test’. Wait for the test to complete.
The primary (upper) display shows the loop impedance.
7. To read the Prospective Earth Fault Current, press the F3 key and
select lK. The Prospective Earth Fault Current appears in amps or kilo
amps in the secondary (lower) display.
8. If the mains is too noisy, Err 5 will be displayed. (The measured value
accuracy is degraded by the noise.) Press the down arrow to display
the measured value. Press the up arrow to return to the Err 5
display.
This test will take several seconds to complete. If the mains is
disconnected while the test is active, the test automatically terminates.
Hi current
If no RCDs are present in the system under test, you can use the high current
Line Earth (L-PE) loop impedance test.
1. Turn the rotary switch to the Z| TRIP position.
2. Connect all three leads to the L, PE, and N (red, green, and blue) terminals
of the tester.
3. Press F1 to select L-PE. The trip symbol appears to indicate that hi current trip
mode is selected.
4. Press F2 to select between Ω and mΩ resolution for the test results. The
mΩ resolution test takes between 30 and 60 seconds to complete.
5. Connect all three leads to the L, PE, and N of the system under test or
plug the mains cord into the socket under test.
6. Press and release ‘Test’. Wait for the test to complete.
The primary (upper) display shows the loop impedance.
7. To read the Prospective Earth Fault Current, press the F3 key and
select lK. The Prospective Earth Fault Current appears in amps or kilo
amps in the secondary (lower) display.
8. If the mains is too noisy, Err 5 will be displayed. (The measured value
accuracy is degraded by the noise.) Press the down arrow to display
the measured value. Press the up arrow to return to the Err 5
display.